Identity is questioned when it is threatened; for immigrants the threat arises from displacement from their mother country to a new home where they are compelled to ask who they truly are. In England they are no longer alone in confronting these questions. With the challenge to multiculturalism from the growth of British-born Islamic extremism - together with anniversaries of the act of union and the election of the Labour government - national identity has leapt from abstract concern to an all-out obsession.

Recent research suggests that people living in England are more likely to define themselves as English than British. Tellingly, black and Asian respondents overwhelmingly preferred to think of themselves as British than English. The very vagueness of Britishness is its greatest attraction, as its bagginess makes it an easier label to wear than Englishness. But what does it mean to be English?

Rather than pondering this from the comfort of his study, the philosopher Julian Baggini spent six months living in Rotherham, in a district that he took to be a statistical microcosm of England. He wanted "to understand the English mind, what we think, what we believe, what we want and what we value". He observes with fascination the behaviour of the English as they drink, eat, gamble, travel and seek partners. He attempts to immerse himself in the culture of the "natives" and win their trust by reading only the Sun and Daily Mail and watching only the highest-rating television programmes.

The idea that we are all middle-class now is, Baggini argues, merely a myth that the English like to believe about themselves. Although the numbers of people who call themselves working-class is declining, he maintains that English culture is still predominantly working-class. It is football rather than cricket that is the national sport, and the most popular television programmes still reflect working-class culture, whether they are soaps, quizzes or entertainments that follow a template straight out of clubland.

This self-deception extends into attitudes to food. Baggini's English may watch Jamie Oliver and Gordon Ramsay, but of the 171 million cookery books bought each year, 61 million are never opened. When a local pub in Rotherham started offering Thai food, a regular complained to Baggini: "We don't want this foreign food. We want traditional stuff like lasagne."

Although Baggini tries to fit in, he is an outsider in this world - a stranger in his own country. The liberal left, which has traditionally identified itself with the white working-class, is, he argues, similarly estranged and out of tune. This is particularly evident with respect to multiculturalism. Rather than championing multicultural integration - which is doomed, since many of us prefer to be around those who are similar to us - Baggini suggests we adopt a position of toleration. In other words, let us all be English in whatever way we choose; as long as your Englishness does not threaten mine, it doesn't matter if it's different. While this has the advantage of simplicity it fails to explain how to respond when a personal identity is welded to a religious and political identity: where and when does tolerance end?

There are times when even Baggini finds his tolerance tested, such as when discussing the popularity of Nuts and Zoo magazines among young men, and plastic surgery among young women. When a fellow drinker suggests the best time to pick up women is when they are too drunk to know what they're doing, Baggini shakes his head, worrying that "sometimes it seems that I am the only person in the country who thinks this kind of attitude is pernicious." Plenty of others, Daily Mail readers included, might share his concerns, but it has little to do with being English.

While the intention might have been to understand the English mind in general, the book is more insightful as a guide to a particular English mind - that of the author. Despite his best efforts Baggini remains endearingly out of place - a middle-class southern intellectual who likes arthouse films and red wine, among those in working-class Rotherham who prefer telly and tea. Yet this is a thoughtful, sympathetic portrait of white working-class life which is essential reading, even if a convincing definition of Englishness ultimately escapes its grasp.

· Sarfraz Manzoor's Greetings from Bury Park: Race, Religion & Rock'n'roll is published by Bloomsbury in June